The goal of this pilot study is to demonstrate age-related differences in lower genital tract risk factors for preterm delivery, by assessing cervical length, vaginal pH, and the concentration & combination of microflora & tissue-destructive factors in the vaginal fluid of pregnant adolescents following treatment for a recognized infection. The results will provide a foundation for a prospective, randomized, controlled antibiotic treatment trial in pregnant adolescents, who are thought to be at increased risk for infection-mediated preterm delivery.